The project consists of several endeavors. Methods are to be worked out for the isolation of Factor VII and Protein C. They appear together in one fraction and can be separated. The procedure requires further modofications. A complete scheme for the separation of many components of the prothrombin complex makes it possible to conserve materials and working time. It seems likely that Factor IX is activated by Factor Xa and further work is needed to rule out possible sources of error. By using purified preparations of 2-Gla-prothrombin, 5-Gla-prothrombin and 7-Gla-prothrombin and various conditions of activation more information on the function of gamma-carboxy glutamic acid might be found. It seems likely that two previously unrecognized plasma proteins have been identified. One of these is called Protein M and the other Protein M-2. The latter functions as an accelerator in a 4-component system consisting of prothrombin plus phospholipid plus Factor Xa plus calcium ions. Protein M functions in a 5-component system consisting of prothrombin plus phospholipid plus Factor Xa plus Ac-globulin plus calcium ions. Protein M is to be tested with purified prothrombin 1, and the atypical purified prothrombins. An attempt is to be made to determine the nature of prothrombin activation with purified Ecarin. For that purpose, prothrombin 1 is to be used as a substrate.